normalize “an empty string” to “the empty string” (#544)

Co-authored-by: Scott O'Hara <[email protected]>

Author: adampage

html-aam/index.html

@@ -3259,15 +3259,15 @@ <h4 id=el-img>`img`</h4>
     </tr>
   </tbody>
 </table>
-<h4 id=el-img-empty-alt>`img` <span class="el-context">(`alt` attribute value is an empty string, i.e. `alt=""` or `alt` with no value in the markup)</span></h4>
+<h4 id=el-img-empty-alt>`img` <span class="el-context">(`alt` attribute value is the empty string, i.e. `alt=""` or `alt` with no value in the markup)</span></h4>
 <table aria-labelledby=el-img-empty-alt>
   <tbody>
     <tr>
       <th>HTML Specification</th>
       <td>
         <a data-cite="html">`img`</a>
         <span class="el-context">(<a data-cite="html/embedded-content.html#attr-img-alt">`alt`</a>
-                attribute value is an empty string, i.e. `alt=""` or `alt` with no value in the markup)</span>
+                attribute value is the empty string, i.e., `alt=""` or `alt` with no value in the markup)</span>
       </td>
     </tr>
     <tr>

html-aam/test.html

@@ -1606,7 +1606,7 @@ <h1 id="title" class="title">HTML Accessibility API Mappings 1.0</h1>
               <th>
                 <a data-type="element" href="https://html.spec.whatwg.org/multipage/embedded-content.html#the-img-element"><code>img</code></a>
                 <span class="el-context">(<a href="https://html.spec.whatwg.org/multipage/embedded-content.html#attr-img-alt"><code>alt</code></a>
-                attribute value is an empty string, i.e. <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
+                attribute value is the empty string, i.e., <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
               </th>
               <td class="aria">
                 <div class="role">
@@ -4137,11 +4137,11 @@ <h1 id="title" class="title">HTML Accessibility API Mappings 1.0</h1>
               </caption><tbody><tr><th>[<cite><a class="bibref" data-link-type="biblio" href="#bib-wai-aria-1.2" title="Accessible Rich Internet Applications (WAI-ARIA) 1.2">wai-aria-1.2</a></cite>]</th><td><a class="core-mapping" href="https://w3c.github.io/core-aam/#role-map-img"><code>img</code></a> role</td></tr><tr><th><a href="https://msdn.microsoft.com/en-us/library/dd373608%28v=VS.85%29.aspx"><abbr title="Microsoft Active Accessibility">MSAA</abbr></a> + <a href="http://accessibility.linuxfoundation.org/a11yspecs/ia2/docs/html/">IAccessible2</a></th><td><div class="general">Use <abbr title="Accessible Rich Internet Application">WAI-ARIA</abbr> mapping</div></td></tr><tr><th><a href="https://msdn.microsoft.com/en-us/library/ms726297%28v=VS.85%29.aspx">UIA</a></th><td><div class="general">Use <abbr title="Accessible Rich Internet Application">WAI-ARIA</abbr> mapping</div></td></tr><tr><th><a href="https://gnome.pages.gitlab.gnome.org/atk/">ATK</a></th><td><div class="general">Use <abbr title="Accessible Rich Internet Application">WAI-ARIA</abbr> mapping</div></td></tr><tr><th><a href="https://developer.apple.com/reference/appkit/nsaccessibility">AX</a></th><td><div class="general">Use <abbr title="Accessible Rich Internet Application">WAI-ARIA</abbr> mapping</div></td></tr><tr><th>Comments</th><td></td></tr></tbody></table></details><details class="map"><summary id="el-img-empty-alt">
                 <code>img</code>
                 <span class="el-context">(<code>alt</code>
-                attribute value is an empty string, i.e. <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
+                attribute value is the empty string, i.e., <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
               </summary><table><caption>
                 <a data-type="element" href="https://html.spec.whatwg.org/multipage/embedded-content.html#the-img-element"><code>img</code></a>
                 <span class="el-context">(<a href="https://html.spec.whatwg.org/multipage/embedded-content.html#attr-img-alt"><code>alt</code></a>
-                attribute value is an empty string, i.e. <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
+                attribute value is the empty string, i.e., <code>alt=""</code> or <code>alt</code> with no value in the markup)</span>
               </caption><tbody><tr><th>[<cite><a class="bibref" data-link-type="biblio" href="#bib-wai-aria-1.2" title="Accessible Rich Internet Applications (WAI-ARIA) 1.2">wai-aria-1.2</a></cite>]</th><td>
                 <div class="role">
                   <a class="core-mapping" href="https://w3c.github.io/core-aam/#role-map-presentation"><code>presentation</code></a>